1. Field of the Invention
The present invention relates to a radiographic imaging device. The present invention in particular relates to a radiographic imaging device that has plural pixels disposed in a matrix, accumulates charge generated by radiation irradiation, and detects the accumulated charge amount as an image data. The present invention also relates to a radiographic imaging apparatus employing such a radiographic imaging device image a radiographic image.
2. Description of the Related Art
Recently, radiographic imaging devices have been put into practice employing a radiographic imaging device of a FPD (flat panel detector), or the like. Such radiographic imaging devices have an X-ray sensitive layer disposed on a TFT (Thin Film Transistor) active matrix substrate, and are able to directly convert X-ray information into digital data. Such FPDs have the merit that, in comparison to with previous imaging plates, images can be more immediately checked and video images can also be checked. Consequently the introduction of FPDs is proceeding rapidly.
Various types are proposed for such radiographic imaging devices. There are, for example, direct-conversion-type radiographic imaging devices that convert radiation directly to charge in a semiconductor layer, and accumulate the charge. There are also indirect-conversion-type radiographic imaging devices that first convert radiation into light with a scintillator, such as CsI:Tl, GOS (Gd2O2S:Tb) or the like, then convert the converted light into charge in a semiconductor layer and accumulate the charge.
A radiographic imaging apparatus is known that has a second photoelectric conversion element (a sensor for AEC control) disposed on the same substrate but independently to pixels having first conversion elements disposed in a conversion section on the substrate for outputting image data (see, for example, JP-A No. 2004-130058). The second photoelectric conversion element (AEC control sensor) is an element employed for detecting the total irradiated amount of radiation incident to the conversion section in order to perform Automatic Exposure Control (AEC). The second photoelectric conversion element is connected via a signal line to a second amplifier (AMP) of a processing circuit section for detecting the total irradiated amount of radiation incident on the conversion section.
However, in the radiographic imaging apparatus described in JP-A No. 2004-130058, the second photoelectric conversion element is disposed over a relatively large region in order to detect the radiation irradiation amount with precision. Namely, the second photoelectric conversion element needs to be made large in order to detect the radiation irradiation amount with precision. However, in cases where the second photoelectric conversion element is made large, the continuously disposed first conversion elements for detecting the image data can no longer be disposed in the region where the second photoelectric conversion element is disposed, or the pixel size of the first conversion elements becomes smaller. As a result, the image detection precision of the radiographic imaging apparatus is reduced.